linux-kernel - [PATCH] tracing: Fix event filters and triggers to handle negative numbers

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Message-Id: <20180823102534.7642-1-ptikhomirov@virtuozzo.com>
Date:   Thu, 23 Aug 2018 13:25:34 +0300
From:   Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Al Viro <viro@...IV.linux.org.uk>,
        linux-kernel@...r.kernel.org,
        Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
Subject: [PATCH] tracing: Fix event filters and triggers to handle negative numbers

Then tracing syscall exit event it is extremely useful to filter exit
codes equal to some negative value, to react only to required errors.
But negative numbers does not work:

[root@...rch sys_exit_read]# echo "ret == -1" > filter
bash: echo: write error: Invalid argument
[root@...rch sys_exit_read]# cat filter
ret == -1
        ^
parse_error: Invalid value (did you forget quotes)?

Similar thing happens when setting triggers.

These is a regression in v4.17 introduced by the commit mentioned below,
testing without these commit shows no problem with negative numbers.

Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster")
Signed-off-by: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
---
 kernel/trace/trace_events_filter.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 84a65173b1e9..2ba449292561 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1299,7 +1299,7 @@ static int parse_pred(const char *str, void *data,
 		/* go past the last quote */
 		i++;
 
-	} else if (isdigit(str[i])) {
+	} else if (isdigit(str[i]) || str[i] == '-') {
 
 		/* Make sure the field is not a string */
 		if (is_string_field(field)) {
@@ -1312,6 +1312,9 @@ static int parse_pred(const char *str, void *data,
 			goto err_free;
 		}
 
+		if (str[i] == '-')
+			i++;
+
 		/* We allow 0xDEADBEEF */
 		while (isalnum(str[i]))
 			i++;
-- 
2.17.1